diff --git a/doc/src/sgml/Makefile b/doc/src/sgml/Makefile
index 4ae7ca2be7..33b72d03db 100644
--- a/doc/src/sgml/Makefile
+++ b/doc/src/sgml/Makefile
@@ -184,8 +184,12 @@ XSLTPROC_FO_FLAGS += --stringparam img.src.path